The present invention relates generally to a rotating machine. More specifically, the present invention relates to structure for attaching terminals to the stator of a rotating machine, e.g., a resolver.
The present invention claims priority from Japanese Patent Application No. 2002-101179, which was filed on Apr. 3, 2002, and which is incorporated herein by reference for all purposes.
Resolvers have been employed in myriad systems where, for example, rotation position detection is required. One known class of resolver is the variable reluctance resolver. In the variable reluctance resolver 500 depicted in FIGS. 5 and 6, multiple magnetic poles 3 protrude from a circular yoke 2 on to which poles a stator winding (not shown) is wound. It will be appreciated that the stator accommodates and receives a rotor (also not shown), as discussed below. See also copending, commonly-assigned U.S. patent application No. 2002/0063491 A1 to Kobayashi et al., which claims priority from Japanese Patent Application No. JP02002171737A.
Still referring to both FIGS. 5 and 6, a stator assembly 520 of a typical variable reluctance resolver 500 is formed by using a first stator magnetic pole assembly 55, which is provided with a component attachment portion 57, and a second stator magnetic pole assembly 56, which assemblies flank respective sides of the circular stator core 1. As discussed below, the core 1 consists of a stack of soft metallic magnetic plates, e.g., silicon steel plates.
In FIG. 5, both ends of the stator core 1 are flanked, and consequently the stator core assembly 520 including the first stator magnetic pole assembly 55, and the second stator magnetic pole assembly 56, are enclosed by a synthetic resin 201 in such a way that the surfaces of the magnetic pole teeth 4 of the stator core 1, i.e., the teeth that face a rotor (not shown), are left exposed. The inside portions of the stationary magnetic pole teeth 4 of the stator core 1 are such that they oppose the outside surface of the rotor (not shown) when the rotor is disposed in the interior of the stator assembly 520.
The first stator magnetic pole assembly 55 and the second stator magnetic pole assembly 56 are joined by the synthetic resin 201, which is forced through multiple fixing holes 203, which are through holes provided in the stator core 1. The synthetic resin 201 forms a uniform circular surface with the inside portions of the stationary magnetic pole teeth 4, which portions are not covered by the synthetic resin 201. In addition, the synthetic resin 201 also partially, if not fully, saturates the windings of the stator assembly 520 in which the stator winding (not shown) is disposed, and secures the stator magnetic pole assemblies 55, 56 to the stator core 1. The stator magnetic pole assembly fixing holes 203 pass through the stator core 1 proximate to the outer periphery of the stator magnetic pole assemblies 55, 56. The resin 201 fills the stator magnetic vole assembly fixing holes 203 completely, encloses the stator magnetic vole assemblies 55, 56, and secures the stator magnetic role assemblies 55, 56 to the stator core 1.
The first stator magnetic pole assembly 55 has a structure in which a component attachment portion 57 is provided, while the second stator magnetic pole assembly 56 lacks a component attachment portion 57. The interior of the component attachment portion 57 is not covered by the synthetic resin 201; a potting material 400 is injected to plug up the exposed portions. A lead wire or lead wire bundle 204 is drawn out from the component attachment portion 57 into which the potting material 400 has been injected; the lead wire bundle is such that it can be externally connected to a wiring harness (not shown).
FIG. 6 is an exploded view of the stator assembly 520 shown in FIG. 5. Multiple stator magnetic pole assembly fixing holes 203 provided in the stator core 1 pass through the stator core 1, which is formed by a laminated stack of steel plates 1a-1n. The synthetic resin 201 penetrates the stator magnetic pole assembly fixing holes 203 and contacts the first stator magnetic pole assembly 55 and the second stator magnetic pole assembly 56 to secure them to the stator core 1. The synthetic resin 201 consists of a material that has a coefficient of thermal expansion of 0.00003/cm/cm/° C., such as PBT glass (30%). The first stator magnetic pole assembly 55 and the second stator magnetic pole assembly 56 each consist of a material that has a coefficient of thermal expansion of 0.00003/cm/cm/° C., such as PBT glass (30%). It will be noted that a coil winding portion 510, which has the same shape and quantity of protrusions as the stationary magnetic pole portion 3 and the magnetic pole teeth 4 of the yoke 2, is provided on each of the stator magnetic pole assemblies 55, 56.
Thus, the first stator magnetic pole assembly 55, the laminated stator core 1, and second stator magnetic pole assembly 56, are stacked such that the stationary magnetic pole teeth 4 provided on the stationary magnetic pole portion 3 of the stator core 1 and the coil winding portions 510 of the first and second stator magnetic pole assemblies 55, 56 are aligned with one another.
In addition to the fastening function provided by the through holes 203 and synthetic resin 201, two component attachment portion fixing holes 401c and 401d are provided in and pass through the laminated stator core 1. When encapsulating the first stator magnetic pole assembly 55 and the second stator magnetic pole assembly 56 with a synthetic resin 201, the synthetic resin 201 passes through additional (and adjacently positioned) through holes 401a and 401b, which are provided in the component attachment portion 57, to further secure the component attachment portion 57 to the stator core 1.
As mentioned above, a stator winding (not shown) is wound around the coil winding, e.g., magnetic poles 3, of the stator assembly 520 assembled as described above using a predetermined winding pattern, and the ends of the windings are connected to attachment pins (also not shown) associated with the component attachment portion 57 and secured to the first stator magnetic pole assembly 55 and second stator magnetic pole assembly 56. Then the stator assembly 520 is enclosed with the synthetic resin 201. The component attachment portion 57 is such that the potting material 400 (see FIG. 5), which has a coefficient of thermal expansion of 0.000046/cm/cm/° C., such as epoxy resin, is injected to plug up the exposed portions, e.g., the attachment pins.
Analysis of this assembly method reveals the following problems. Specifically, in the draw-out structure of a conventional lead wire, the structure is such that after the stator winding is wound, the ends of the winding are connected to attachment pins (not shown) of the component attachment portion 57, and the lead wire is drawn out to the exterior of the stator assembly 520. The component attachment portion 57 becomes an integral structure with the first stator magnetic pole assembly 55, which is formed of resin. For this reason, when an external force is applied to the component attachment portion 57, there are cases where the component attachment portion 57 ruptures at its boundary with the first stator magnetic pole assembly 55. In addition, when an external force is applied to the component attachment portion 57, an external force is also applied to the stator winding that is wound on the coil winding portions 510 of the final stator assembly 520, since it is an integral unit with the first stator magnetic pole assembly 55. Given that external force, there are cases where the windings short, and resolver reliability decreases. In addition, when the first stator magnetic pole assembly 55 becomes an integral structure with the component attachment portion 57, its structure becomes complex. Moreover, the shapes of the first and second magnetic pole assemblies 55, 56 differ from one another. Since there is a need to use stator magnetic pole assemblies that have respectively different shapes, it is difficult to reduce resolver prices.
What is needed is a resolver terminal attachment structure that is highly reliable. Moreover, what is needed is a resolver terminal attachment structure that permits construction of a low cost resolver.